Hybrid structure solution for the A400M wing attachment frames

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Matthijs Plokker / Derk Daverschot - ICAF 2009
20/05/2009
Hybrid structure solution for the A400M wing
attachment frames
From concept study to structural justification
ICAF 2009, Rotterdam
Presented by
Matthijs Plokker / Derk Daverschot
Fatigue and Damage Tolerance, Airbus
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 2
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Contents
• Introduction
􀀗A400M – General
&#1048599roblem description
• Concept study
• Implementation
􀀗Design & Material
&#1048599roduction Process
􀀗Quality Assurance
• Structural Qualification
􀀗Requirements
􀀗Analysis
􀀗Test
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 3
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A400M – General
A400M General Configuration
Typical for A400M and deviating from common Airbus A/C:
•Turboprop engines
•High wing
•T-tail
•MLG configuration
•Cargo Ramp & Door
•Militairy Systems:
Cargo Handling system, AAR
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 4
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A400M – General
• Comparison to other militairy airlifters
A400M C160 Transall C130J Hercules
Payload 37 t 16 t 22 t
MTOW 130 t 50 t 70 t
Range 6 500 km 1 800 km 4 500 km
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 5
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A400M – General
• Comparison to „other airlifters“
length [m] 45 59
wingspan [m] 42 60
height [m] 15 17
A400M C160 Transall C130J Hercules A330-200F
Payload 37 t 16 t 22 t 69 t
MTOW 130 t 50 t 70 t 228 t
Range 6 500 km 1 800 km 4 500 km 7 400 km
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 6
© AIRBUS DEUTSCHLAND GMBH. All rights reserved. Confidential and proprietary document.
A400M – General
• Strategic airlift mission capability:
􀀗 Long range (to allow deployment flexibility),
􀀗 High cruise speed,
􀀗 Large cargo hold dimension and volume combined with.
􀀗 High payload (to match the whole range of modern military vehicles, helicopters,
containers and heavy engineering equipment),
􀀗 Flexible cargo handling system (to allow rapid internal configuration changes for different
types of loads) and the possibility of.
􀀗 In-flight refueling;
• Tactical airlift mission capability:
􀀗 Low speed characteristics (for airdrop and tactical flight).
􀀗 Short soft field performance,
􀀗 Autonomous ground operation, aerial delivery of paratroops and cargo loads and.
􀀗 High survivability (damage-tolerant design of airframe and systems);
• Aerial tanker mission capability:
􀀗 2 or 3 point refueling system and.
􀀗 Wide altitude/speed flight envelope (allowing refueling of both helicopters and fighter aircrafts).
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 7
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A400M – General
• Aircraft Target Operational Usage
• 67% logistic - 20% tactical - 12% crew training
• Tactical mission Low Level Flight
-> 1½ hr at 50m altitude
• Design Life: 10 000 FC / 30 000 FH / 30 years
• Inspection Threshold: 5 000 FC / 15 000 FH
• Inspection Interval: 2 500 FC / 7 500 FH
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 8
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Wing attachment frames
Center Fuselage:
I/F with wing and MLG
Wing attachment frames
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 9
© AIRBUS DEUTSCHLAND GMBH. All rights reserved. Confidential and proprietary document.
Problem description
• Problem description:
• Investigation showed that main frame under rear wing attachment is SLP
structure instead of MLP.
• Hence, frame had to be inspected on small cracks, instead of failed part.
Design criterium had to be stricter, resulting in low allowable DT-stresses
to ensure slow crack growth
• Design had to be improved => severe weight impact when concept of
integral frame would have been kept.
Rear wing attachment
Severe Wing Spectrum introduced in this
frame and surrounding structure.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 10
© AIRBUS DEUTSCHLAND GMBH. All rights reserved. Confidential and proprietary document.
Problem description
• Wing spectrum caused in frame inner flange below rear wing
attachment:
1. High Fatigue Stresses in inner flange
2. High tensional static loads
• Resulting in:
1. To meet inspection interval detecable crack length 1-2 mm
– Risk due to low probability of detection
2. Critical crack length is extremely small (enhanced by brittle alloy)
• Risk on Multiple Element Damage (MED) due to similar high stress level
in neighbouring frames
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 11
© AIRBUS DEUTSCHLAND GMBH. All rights reserved. Confidential and proprietary document.
Concept study
• Study was carried out on improvement of the main frame looking at:
􀀗 Safety (Inspectibility, DT-behaviour)
􀀗 Weight
􀀗 Cost
• 3 options were investigated:
1. Thickening of the aluminium inner flange to reach an acceptable stress
level.
2. Riveted Titanium strap attached to the inner flange.
3. FML strap adhesively bonded to the inner flange.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 12
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Concept study
• Coupon test program performed to investigate crack growth behaviour
of FML reinforced inner flange.
• The test results showed a constant crack growth rate for a wide range
of crack lengths. This is due to the „crack bridging“ effect.
With metal isotropic material an increasing crack growth rate will be
found for longer cracks.
At same stress level only FML
strap can meet the inspection
requirement.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 13
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Concept study - FML strap
Concept of FML Reinforcement:
􀀗The aim of the bonded FML-strap is to control both the fatigue
crack growth behaviour of the frame and the residual strength
capability of the hybrid design.
􀀗The FML strap will retard or stop any potential fatigue crack in the
frame.
Frame Inner Flange
FML Strap
„Crack Bridging“ effect analogue to GLARE
Cross-section
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 14
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Concept study - Conclusions
Results of concept study:
• FML reinforcement was favourised:
􀀗Lowest weight
􀀗Meeting best all DT requirements. Static requirements were fulfilled as
well.
􀀗Relatively low costs per lost kg per A/C.
• Titanium reinforcement:
􀀗Heavier compared to FML strap solution
􀀗Could not satisfy with meeting all DT-requirements
• Integral frame:
􀀗Could not meet DT requirements with acceptable weight.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 15
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Concept study - Conclusions
Integral - -
Aluminium
FML Strap ++ ++
Titanium Strap + --
Effort to detect
cracks
Weight
opportunity
Option
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 16
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Concept study - Conclusions
• In general the FML reinforcement bonded application is a solution for
structural parts that are highly loaded under tension.
Without FML-reinforcement this structural part would be a SLP or a
structure with poor damage containment feature at the most.
• Bonded FML-reinforcement is normally optimal for SLP frames,
regarding:
1. Safety -> larger critical crack length, reducing risk of MED.
2. Weight -> Higher Allowable Stresses for DT
3. Cost -> Less inspection with lower inspection level
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 17
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Implementation - Design & Material
• The FML-Strap is bonded to the inner frame flange in an area which is
fatigue design-driven.
• The upper end run-out is not a fatigue-driven location.
Run-out
Glare2A
•Thickness ratio inner flange to
FML strap is 1:2
•Glass-Fibres are unidirectional
in hoop direction (GLARE2A)
•Strap Lay-up according to
A380 Principles
Loft
web
inner flange
outer flange
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 18
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Implementation - Design & Material
• Anti-peeling fastener
􀀗Not load transfering rivet
􀀗Reducing net-section
􀀗Introduces fatigue sensible locations
􀀗Request based on CS23.573(a) (although applicable to smaller
aircraft and subparagraphe for composite material)
Bonded strap
with anti-peeling
fasteners
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 19
© AIRBUS DEUTSCHLAND GMBH. All rights reserved. Confidential and proprietary document.
Implementation - Design & Material
CS23.573 (a) (5)
„(5) For any bonded joint, the failure of which would result in catastrophic loss of
the aeroplane, the limit load capacity must be substantiated by one of the
following methods:-
(i) The maximum disbonds of each bonded joint consistent with the capability to
withstand the loads in subparagraph (a)(3) must be determined by analysis,
test, or both. Disbonds of each bonded joint greater than this must be
prevented by design features; or
(ii) Proof testing must be conducted on each production article that will apply the
critical limit design load to each critical bonded joint; or
(iii) Repeatable and reliable nondestructive inspection techniques must be
established that ensure the strength of each joint.“
(i) -> Possible
(ii) -> Not practical/economical
(iii) -> Not feasible
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 20
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Implementation - Production Process
1) Production of FML-panel 2) FML-straps milled out of panel
5) FML-strap bonded to frame
3) Frame pretreated with CAA 4) Frame primed with BR127
Distortion due to delta in CTE
First assemblies acceptable, some frames
have to be shimmed on shell level assy.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 21
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Implementation - Production Process
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 22
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Implementation - Quality Assurance
Inspection during manufacturing:
Step 1: Manufacturing of FML-strap laminate
Inspection of the laminate by ultrasonic through transmission in squirter technique
Step 2: Bonding of FML-strap to Aluminium frame
Inspection of bond line by manual ultrasonic through transmission technique
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 23
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Implementation - Quality Assurance
Principle of the ultrasonic through transmission method – single channel mode
water beam
Water jet
water supply
receiver transducer
Squirter technique
x
z
• Basic principle: ultrasonic through transmission method in squirter technique
• Both side accessibility of the inspected part required
• Complete and reproducible documentation of test data
• Display mode: C-scan (top-view)
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 24
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Implementation - Quality Assurance
Principle of the ultrasonic through transmission method – single channel mode
• Information on location and size of defect provided
• Information on defect depth not provided
signal amplitude [dB]
measured value result: C-scan image
x
z
•Display mode: C-scan (top view)
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 25
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Implementation - Quality Assurance
Principle of manual ultrasonic through transmission technique – single
channel mode using inspection tongs (for in-production and in-service
application)
• Basic principle: ultrasonic through transmission method in general comparable to
through transmission method in squirter technique, manual movement of the
transducers
• both-side accessibility required
• Display mode: A-scan
• A-scan: Assessment of indications by means of sound attenuation relative to the
defect-free surrounding area
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 26
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Structural Qualification - Requirements
Basis for Certification
• JCRI (JAA Certification Review Item) is a selected identified item of the
civil CS regulation with rules and policies established in other civil
programs.
• MCRI (Military Certification Review Item) is a selected extension of the
civil CS regulation with rules and policies derived from military
regulations and standards.
• Note: Although A400M is a militairy transport aircraft, the basis for
certification is the civil CS25 – former JAR25.
􀃎Hence CS25.571 (b) is applicable, which implies requirement of
Damage Tolerant design.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 27
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Structural Qualification - Analysis
• Main Frame with FML-Strap is a Structure with Damage
Containment Feature (DCF).
• Calculated Components
􀀗 Justification of FML strap (run-out and highest stressed location)
􀀗 Justification of Frame Inner Flange
• Failure Criteria
􀀗 F&DT: Fatigue, Crack Growth, No Defect Growth, Residual Strength.
􀀗 Static: Material Strength, Stability
Analyses supported by Test Evidence
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 28
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Structural Qualification - Analysis
• Fatigue crack growth:
􀀗Load divided between Strap and Inner flange by product of
stiffness and area
􀀗Crack growth corrected for “crack bridging” by additional
function α
􀀗Edge cracks from bore holes and edges calculated
Strap bridging versus crack length
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 10 20 30 40 50 60 70 80 90 100
c ra c k le ng t h a (mm)
S t rap bridging funct ion Expon. (S t rap bridging funct ion)
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 29
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Structural Qualification - Analysis
• Residual strength analysis
• Conclusion: Introducing an significant initial centred unbonded zone does not
lead to delamination growth under tensile as well as compressive limit load
neither. Final maximum size of acceptable delamination could not be found
due to limits of the model.
􀃎Based on this outcome the rivet pitch has been defined.
Frame stress
distribution at
ultimate positive
moment
Frame stress
distribution at
ultimate negative
moment
Frame Inner Flange with bonded
reinforcement modelled.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 30
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Structural Qualification - Test
• Full-scale Fatigue Test with MSN5001
• Frames on Left Hand (LH) and Right Hand (RH) with FML straps:
􀀗 LH side: normal series standard
􀀗 RH side: small artificial delaminations in frame-strap bondline and Glare
• Simulating 2.5 DSG (25.000 FC)
􀀗 Planned for Feb. 2010- Feb. 2011
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 31
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Structural Qualification - Test
Overview Static component tests (three)
Aim of the static frame bending test series is to evaluate the bonding of the FML-strap in
the region of the highest stress level and at the run-outs.
1. Frame with continuous Glare strap
– 1 specimen
– Loaded with negative bending moment, ultimate load
– Small artificial delaminations in frame-strap bondline
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 32
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Structural Qualification - Test
2. Frame with run-out of Glare strap,
– 2 specimens
– Loaded with positive/negative bending moment, ultimate load
– Small artificial delaminations in frame-strap bondline
3. Frame with continuous Glare strap
– 2 specimens
– Loaded with positive/negative bending moment, limit load
– Large artificial delamination in frame-strap bondline (determined from
FE-analysis)
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 33
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Structural Qualification - Test
Overview F&DT component tests (two)
1. Frame with continuous Glare strap
– 1 specimen
– Spectrum of 3 DSG and limit load (tension+compression)
– Initial flaws installed (1.27mm through cracks)
– Small artificial delaminations in frame-strap bondline
Strap
Frame inner
flange
Frame outer
flange
P4
P1 P7
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 34
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Structural Qualification - Test
2. Frame with run-out of Glare strap
– 1 specimen
– Spectrum of 3 DSG and limit load (tension+compression)
– No initial flaws
– Small artificial delaminations in frame-strap bondline
– Specimen without artificial delamination for crack initiation and crack
propagation investigation
FML-straps
Frame inner flange
Frame outer flange
P4
P1 P7
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 35
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Structural Qualification - Test
• Overview Coupon Tests
• Material and static coupon tests
– Tensile test thick Glare2A
– Compression test Glare2A
– Blunt notch test Glare2A
– Bearing test Glare2A
• Fatigue coupon tests
– Bonded+riveted specimens
– 20 specimens with/without cold worked holes
• Crack growth tests
– Coupon tests by external company in development phase
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 36
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Summary
• FML strap establishes a safer, damage tolerant design of a highly
loaded frame.
• The new application has been introduced with an extensive
qualification program. All disciplines have to coorperate closely.
􀀗Structure engineering
􀀗Material
􀀗Quality Assurance
&#1048599rocess
• The first Production and Assembly has been succesfull.
Matthijs Plokker / Derk Daverschot - ICAF 2009 20/05/2009 Page 37
© AIRBUS DEUTSCHLAND GMBH. All rights reserved. Confidential and proprietary document. Thanks for your attention/
Bedankt voor uw aandacht
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© AIRBUS DEUTSCHLAND GMBH. All rights reserved. Confidential and proprietary document.
© AIRBUS DEUTSCHLAND GMBH. All rights reserved.
Confidential and proprietary document.
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property of AIRBUS DEUTSCHLAND GMBH. No intellectual
property rights are granted by the delivery of this document or
the disclosure of its content. This document shall not be
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